George w



. l @who tats @anni @frn GEORGE W. RAWSON, OF CAMBRIDGrElORT, A SSIGNOR TO .HIMSELF AND l MICHAEL HITTINGER, OF SOMERVILLE, MASSACHUSETTS.

Leners Pfam No.r 82,751, daad october e, 186s.

IMPROVEMENT IN CUT-OFI FOR STEAM-ENGINES.

TO ALL PERSONS TO WHOM THESE PRESENTS MAY' COME: Be it known that I, .GEORGE W. RAWSOiLof Cambridgeport, in the county of Middlesex, and State of Massachusetts, have invented a new"and useful Improvement in the Variable Cnt-OE for Steam-Engines; and

'I do hereby declare the same to be fully described in the following specification, and represented in the accompanying drawings, of which- Figurel denotes an elevation ofa slide-valve and the interior of a steam-chest, as provided with my invention.

Figure 2 is a longitudinal and horizontal section of the same.

My present improvement has reference to the subject of Letters Patent, No. 70,743, dated November 12, 1867, and-granted to myself and Michael Hittinger on an'invention Amade by me. v

In carrying out my former invention, I employed rotary valves on the cut-od. It has been found that they are objectionable on account of the noise generated by them when closing down upon their seats, such noise being similar to that made by, the tappets of steam-engine valves.

In order to get rid of the noise, I employ, in the first place, slide-valves for the cut-oliL1 valves, and move each of them in one direction by a chain, and stop the movement in the opposite direction by another chain, and by an arrangement, as hereinafterdescribed, I eifect a steam-balance of the cut-off valves prior to the slide-valvesbeing moved relatively thereto. i i

In such drawing, A denotes the steam-chest, and B the slide-valve thereof. Such steam-chest is Vto be furnished with ports of induction and eduetion, a Z2', to communicate with the engine-cylinder and the exhaust-Y pipe thereof. The seat of each set of these ports is raised abo-ve the bottom, d', of the steam-chest, orformed on a projection, c', raised thereon, in manner as shown in iig. 2, the same being in order that the slide-valve B, just prior to a. movement of the cnt-oh" slide e, may pass over or beyond the edge of the seat c', so Aas to cause steam from the chest to flow into the chamber, e', of the valve B, and against the bars ofthe valve e, and Vthus balance the force by which the cut-off valve may be pressed down upon its seat. Y

The slide-valve, arranged on its seats as represented,'is to be moved longitudinally back and forth by a'. rod, a, jointed to a connecting-rod, b, worked by an eccentric in the ordinary way. The slide-valve has two' exhaustchambers, d d, and two induction-chambers, e, arranged in it in manner as representedfeacb of the chambers, e', being open to the cut-off valve ein manner as shown in fig;` 2. I

The two cut-oli` slide-valves ee have rods or bars-jy, projecting from them in manner as represented', these rods beingA supported by andlso'a's to be capable of sliding lengthwise in two projections, L k, extended from the slide-valve. l

.Encompassing and attached to each of the said rods or bars gg is a helical spring, c,- which, by pressure against the next adjacent projection L, operates to move the bar in amanner to close the cut-off valve.

Furthermore, each ot' the slide-bars g .has a notch, Z, for the reception of one of two pawls or latches, m m, which are hinged to the two projections L 7L, and are connected by a helical spring, 1t, axedto arms x z projecting from the pawls. l l

Between the t-wo pawls` and affixed to a vertical slide-rod, o, is a pawl-tripper or cam, p, whose two lower edges are arranged at an obtuse angle with each other.

The rod, o, of tbe pawl-tripper is to be so applied to a steam-engine governor as to be raised and lowered by it, the same being so that as the speed ofthe engine or governor may be increased, the pawl-tripper may be depressed, it being raised when the speed may slacken.

A chain, r, connects each of the cut-oil" valves with the next adjacent projection h. Another chain, s, also i connects the said valve with the rod. It is not necessary for the chains s to be connected with the rod o, as

they may be fastened to a projection from the ste'iam-chesti A The chain s, when strained tight, holdsthe cnt-oii1 valves stationary in order that the main valve may move relatively thereto, so as to enable steam from the chest to l'ovf` through the cut-oil` valve and the main valve. The chain r holds the cut-o valve closed on the ports ofthe main valve under the pressure of the next adjacent spring 7c.

While the slide-valve B may be'moving toward either end ofthe steam-chest, the chain s, when drawn taut, will bring its cut-oil` valve e to a stand-still. The slide B continuing to move, its ports will be opened, and the next adjacent pawl will catch into the notch oi' the slide-bar of the cut-olf valve, and thereby hold the euto` stationary relatively to the slidevalve,the ports of the slide-valve being open. During the next movement of the slide-valve, that is, in the opposite direction, the pawl last mentioned will be carried against the next adjacent inclined face of the tripper, and by it will be forced out of the notch, so as to enable the cut-off valve to be closed by the action of its spring.

In this manner, the two cut-off valves will be alternately operated, the closing of each upon the ports of the slide-valve being effected sooner or later as the position of the tripper may be varied by the governor.

Just before each ofthe cut-offs is brought to a stand-still by its cha-in, s, the slide-valve B will have moved toward the next adjacent end of the steam-chest, so as to carry a small portion ofthe passage c a little beyond the seat'projection c', and thus enable steam from the steam-chest to ow into the passage e', and thereby effect a'counter-pressure on the cut-o` to balance the pressure, which otherwise would operateto force the cut-o` so closely upon the slide-valve as to create great friction between the two, and materially increase the power required to move the slide-valve. p

From the above, it will be seen that, instead of using stops, such as are marked r .y in the drawings of the patent to which allusion has been hereinbefore made, and such as are ltherein shown as applied to the valveseats, I employ, with the cut-off, chains to arrest their movements. These chains, when properly made, will make no noise of any consequence at the time of being drawn straight. Consequently, I herein make no claim to the subject or subjects as claimed in the aforesaid patent.

The arrangement and combination ofthe stopping-chains with the s teani-chest, the sliding, main, and eut-oli` valves, the springs 7c 1, the rods g g, the pawls or catches m m, and the. tripper p, to be applied to a `governor, the whole being to operate in manner as described.

Also, the arrangement ofthe valve-seat projections c', or the equivalents thereoi, in relation to the steamchest A, the main and cut-cti` slide-valves-B e e, the stopping-chains, the springs k 1:, the cut-off valve-rods g g, the pawls m, m, and the tripper p, the whole being as specified, the valve-seat projections enabling the steam to effect the balancing of the cnt-oil` valves, as explainedeno. W. nAwsoN.

Witnesses R. H. EDDY, F. I. HALE, Jr. 

